Seafood and Seafood Allergens

"Seafood" General term that includes finned fish, crustacean, and mollusks
Vertebrate finned fish All FDA-regulated manufactured food products that contain fish as an ingredient are required by U.S. law to list the specific fish on the product label.	"Shellfish" Includes crustaceans and mollusks
	Crustaceans All FDA-regulated manufactured food products that contain a crustacean shellfish as an ingredient are required by U.S. law to list the specific crustacean shellfish on the product label.	Mollusks Not considered major allergens under food labeling laws and may not be fully disclosed on a product label
Examples
Salmon Tuna Cod Bass Swordfish Etc.	Barnacle Crab Crawfish (crawdad, crayfish, ecrevisse) Krill Lobster (langouste, langoustine, Moreton bay bugs, scampi, tomalley) Prawns Shrimp (crevette, scampi) May also be found in Bouillabaisse Fish stock Glucosamine seafood flavoring (e.g., crab or clam extract) Surimi	Abalone Clams (cherrystone, geoduck, littleneck, pismo, quahog) Cockle Cuttlefish, cuttlefish ink Limpet (lapas, opihi) Mussels Octopus Oysters Periwinkle Scallops Sea cucumber Sea urchin Snails (escargot) Squid (calamari) Whelk (Turban shell) May also be found in Bouillabaisse Fish stock Glucosamine seafood flavoring (e.g., crab or clam extract) Surimi Note that the phylum Mollusca is categorized into Gastropoda (snails, abalone), Cephalopods (squid, octopus), and Bivalvia (scallops, mussels)
Allergens
Major allergen is beta-parvalbumin Resistant to degradation by heat, proteolytic enzymes, chemical denaturation (nevertheless it is denatured by the canning process) Concentration of parvalbumin may be higher in white flesh fish (e.g. cod) vs. darker flesh (tuna), therefore darker fish are considered to be less allergenic Allergy to fish roe has been reported	Major allergen is tropomyosin Heat stable Other allergens include: Arginine kinase Myosin light chain (1 and 2) Sarcoplasmic binding protein Troponin C Triosephosphate isomerase Shrimp at allergen.org Sensitization to a particular shrimp species (while tolerating others) can occur, presumably due to unique allergens	Major allergen is tropomyosin Heat stable Other proposed allergens include: Arginine kinase Hemocyanin Myosin heavy chain Amylase

Seafood Allergen Cross-reactivity

Differential Diagnosis

IgE-mediated allergy or infection by Anisakis simplexfish parasite
- Cooking at temperatures for at least 20 min above 60°C or storage in industrial freezers is required to kill the parasite
- Signs of anisakiasis depend on where in the GI tract the larva is deposited and may develop as a result of an inflammatory response to infection
IgE-mediated allergy to spices or other foods eaten with fish
Cross-contamination of food allergens
- Fish contaminated with shellfish (and vice versa) during preparation (e.g. via shared utensils/cutting boards in restaurant kitchens)
- Soy, milk, or other proteins added to canned seafood
Scombroid fish poisoning and other marine toxins:

Toxin-associated disease (toxin)	Location	Seafood affected	Symptom Onset	Symptoms
Ciguatera (ciguatoxins)	Most originate in tropics/subtropics	More than 400 species; predominantly reef dwelling tropical fish such as barracuda, moray eel, amberjack, grouper, mackerel, parrot fish, red snapper	30 min - 4 h	Gastroenteritis, neurologic, cardiovascular, fatigue and malaise
Paralytic shellfish poisoning (saxitoxins)	Primarily temperate climates, northeast and northwest coasts in United States	Most commonly bivalve molusks such as clams, oysters, and mussels	5 - 30 min	Neurologic - can progress to paralysis and respiratory failure
Neurotoxic shellfish poisoning (brevetoxins)	Southeast coast of United States, Gulf of Mexico, northern Spain, eastern Mediterranean, Japan, New Zealand	Shellfish (often mussels, clams)	30 min - 3 h	Gastrointestinal, neurologic, pulmonary
Diarrheic shellfish poisoning (okadaic acid, dinophysistoxins, pectenotoxins, yessotoxin)	Worldwide; major outbreaks in Japan, Scandinavia, France, Spain, Chile, Uruguay, Nova Scotia	Shellfish (often mussels, clams, scallops)	30 min - 6 h	Gastroenteritis
Pufferfish (tetradotoxin)	Most commonly in Japan; rare cases in United States	Pufferfish (Fugu)	10 - 45 min	Neurologic - can progress to paralysis and respiratory failure
Amnesic shellfish (domoic acid)	First recognized off the coast of Prince Edward Island, Canada	Shellfish (often mussels, clams, crabs), anchovies	15 min - 38 h	Gastroenteritis, neurologic
Possible Estuary- Associated Syndrome (PEAS)	Has been found in the Tar-Pamlico and Neuse River estuaries of North Carolina and in the Pocomoke River on Maryland's eastern shore	Various		Respiratory and eye irritation, neurocognitive

Diagnosis

Test	Shellfish	Finned fish
SPT	SPT with commercial extracts and fresh food typically has a high negative predictive value	SPT with commercial extracts and fresh food typically has a high negative predictive value Boiled extracts may be more allergenic than raw, most commercial extracts include boiled shrimp allergen
In-vitro IgE assays	sIgE (Phadia ImmunoCap) to: Various fish species (see catalog) Beta-parvalbumin rCyp c 1 - carp rGad c 1 - cod	sIgE (Phadia ImmunoCap) to: Various shellfish species (see catalog) rPen a 1 - shrimp tropomyosin In one study, sIgE to shrimp tropomyosin (via an ELISA method) was equally sensitive (~70%) but more specific (92%) than SPT (64%) or sIgE to whole shrimp (75%) in predicting positive shrimp food challenges in dust mite sensitized patients (but only 22% of patients had history of reaction to shrimp) rDer p 10 - dust mite tropomyosin ISAC to tropomyosins (Phadia ImmunoCap) rAni s 3 - Anisakis nBla g 7 - Cockroach rDer p 10 - Dust mite rPen a 1 - Shrimp nPen i 1 - Shrimp nPen m 1 - Shrimp
Oral Food Challenge	Results of OFC may be inconsistent due to species of seafood used, method of preparation (boiled vs. raw), incomplete digestion due to acid blocking medications, allergies only to specific components of the seafood (white vs. dark meat, crab shell, fish roe) *

Shellfish Allergy Management (Sicherer)

Patient type	Management
Anaphylaxis (life threatening) to shellfish	Avoid ALL shellfish Avoidance of finned fish is not necessary (unless patient also has an allergy to fish) If choosing to eat finned fish, be aware of cross-contamination with shellfish during preparation Avoid restaurants or prepare fish at home
Non-life threatening reaction to shellfish	Avoid specific type of shellfish that caused the reaction (e.g. shellfish A) If ingestion of another type of shellfish is desired (shellfish B), consider further evaluation: SPT to shellfish with commercial extract (consider fresh prick to prick), if negative, allow home ingestion (consider office ingestion or OFC), if SPT positive, avoid shellfish B (vs. cautious OFC) If patient tolerated eating shellfish B at home afterreacting to shellfish A, may continue ingesting shellfish B If allowed to eat another type of shellfish, be aware of cross-contamination during preparation; avoid restaurants, prepare shellfish at home Avoidance of fish is not necessary (unless patient also has an allergy to fish) If choosing to eat fish, be aware of cross-contamination with shellfish during preparation Avoid restaurants, prepare fish at home

Finned Fish Allergy Management (Sicherer)

Patient type	Management
Anaphylaxis (life threatening) to fish	Avoid ALL fish Avoidance of shellfish is not necessary (unless patient also has an allergy to shellfish) If choosing to eat shellfish, be aware of cross-contamination with finned fish during preparation Avoid restaurants, prepare shellfish at home
Non-life threatening reaction to fish	Avoid specific type of fish that caused the reaction (e.g. fish A) If ingestion of another type of fish is desired (fish B), consider further evaluation: SPT to fish B with commercial extract (consider fresh prick to prick), if negative, allow home ingestion (consider office ingestion or OFC), if SPT positive, avoid fish B (vs. cautious OFC) If patient tolerated eating fish B at home after reacting to fish A, may continue ingesting fish B Patients who react to fresh tuna/salmon typically tolerate them in canned form. If an individual has reacted to fresh tuna/salmon and is interested in eating them canned, additional SPT/OFC are suggested. If allowed to eat another type of fish, be aware of cross-contamination during preparation; avoid restaurants, prepare fish at home. Be aware that up to 25% of fish in stores/restaurants may be mislabeled. Avoidance of shellfish is not necessary (unless patient also has an allergy to shellfish) If choosing to eat shellfish, be aware of cross-contamination with finned fish during preparation Avoid restaurants, prepare shellfish at home
Reaction to canned fish only (fresh fish tolerated)	Allergy isolated to canned fish is rare Some brands of canned tuna contain soy or milk proteins (and may apply to other canned fish) Canned fish could be contaminated with shellfish during processing